William A. Yost
Parmly Hearing Inst., Loyola Univ. of Chicago, 6525 N. Sheridan Rd., Chicago, IL 60626
A new selective attention procedure was used to measure modulation detection interference (MDI) in which listeners determined if a sinusoidally amplitude modulated probe tone (500 ms and 4000 Hz) had a depth of modulation (ten modulation depths were used) greater than or less than a cue tone (the same as the probe) presented with a depth of modulation of -15 dB (20 log m). Four conditions were tested: (1) probe alone (PA)---probe presented in isolation, (2) unmodulated masker (UM)---an unmodulated 1000-Hz masker presented simultaneously with the probe, (3) modulated masker (MM1)---masker modulated at different rates and with the same envelope phase as the probe, and (4) MM2 condition---masker modulated with an envelope 180(degrees) out of phase with that of the probe. In the MM conditions, the modulated masker was presented with the same ten depths of modulation as the probe. The probe and masker were simultaneously presented, each modulated with one of the ten depths of modulation randomly chosen from trial to trial. The data were analyzed in terms of the weight given to the masker tone while the listener determines probe modulation depth. A weight of 1.0 indicates a synthetic listener in that he/she is unable to hear out the modulated probe in the presence of the modulated masker, and a weight of zero indicates an analytic listener in that he/she can hear out the modulated probe. The results will be discussed in terms MDI and the perceptual grouping of spectral components based on common patterns of amplitude modulation. [Work supported by a Program Project grant from The National Institute on Deafness and Other Communication Disorders, NIDCD.]